Frunching is the act of breathing through ones anus as their lungs reside in their rectum rather than their chest area, an unnatural birth defect caused by believing in the effects of "astrology," a fictional form of witchcraft.
"Yo bro, zak's mad Frunching right now, we just figured out he was born with the Frunch-breath-disorder. (FBD)"
Going to your girlfriends house for Frunch and her ex-in-laws just walk in on you during your nooner.
Yo, my gurl invited me over for frunch and just as she gotnaked her ex-in-laws just walked into her house, turned into Frunch and Company. Lock that door, bro